…. Putting cache on shared storage could work but that is extra complication. There are cases when file cache works pretty well – for example caching full… often. Cache Invalidate With this apporach you invalidate or remove objects in cache once underlying information is updated. This is how MySQL Query Cache works by…
Post: Implications of Metadata Locking Changes in MySQL 5.5
February 1, 2013 By 9 Comments
… Locking was changed, starting MySQL 5.5.3. Let’s see how this works now. Metadata Locking behavior starting MySQL 5.5.3 Starting… Locking and Query Cache How does metadata locking behave with query_cache? That is an important question. If Query Cache is enabled and the… operation waiting, will block. Why? Because MySQL sees that the old entries in the Table Cache have to be invalidated, and any…
Post: MySQL 4 to MySQL 5 Upgrade performance regressions
June 6, 2007 By 8 Comments
… was MySQL 5.0 broken group commit bug. First I should note I am extremely unhappy how MySQL handled this problem. While working for MySQL we spotted this problem early in MySQL 5.0 release cycle… the customers I worked with indeed had battery backed up cache on their system… it just was in “write through” cache policy, so…
Post: Cache Performance Comparison
August 9, 2006 By 74 Comments
… APC cache will not work and results will be wrong. So what is about results and how we can use them for MySQL Performance tuning ? Not surpising associative array cache performs the best, almost… file cache to work you need file named “test” containing “MyTestString” 2) You need to create table test.test for MySQL Cache to work CREATE…
Post: How does MySQL Replication really work?
January 9, 2013 By 9 Comments
… we have one that covers the very basics of how MySQL replication really works on the high level. Or it’s been so… aspects of MySQL replication, but my main focus will be the logistics – how replication events are written on the master, how they are… date will mostly be reading events that are still cached in OS cache on the master, so there is not going to…
Post: Should we give a MySQL Query Cache a second chance ?
April 10, 2011 By 64 Comments
… core of original implementation which appeared in MySQL 4.0 Query Cache was designed to work with single core systems and relatively small… invalidation is enough. Improve Manageability What is in the MySQL Query Cache ? How many hits did we get for this query item ? Right… hard to understand how exactly MySQL Query Cache is working in many cases. This however can be improved and data about Query Cache content and…
Post: Cache Miss Storm
September 10, 2010 By 30 Comments
… or take a look at MySQL Slow queries – which is good enough if you populate each cache item with single query. Optimize… cache to reflect it is being updated right now so you’re better wait rather than starting populating it. For MySQL Query Cache… been implemented so far. Pre-Populate the cache In some cases you can’t change how caching works easily, especially if it is built…
Post: Troubleshooting MySQL Memory Usage
March 21, 2012 By 5 Comments
… Check for Table Cache Related Allocations There are cases when MySQL will allocate a lot of memory for table cache, especially if you… memory usage you might look at how it uses MySQL to identify potential causes. Is it working with large blobs ? Using user variables… look at information_schema to see how much memory is being used by current MEMORY tables: mysql> select sum(data_length+index…
Post: MySQL 5.6 vs MySQL 5.5 and the Star Schema Benchmark
March 11, 2013 By 7 Comments
… little tuning was done. The goal was to see how MySQL 5.6 performs out-of-the-box as compared…10 array with 512MB write-back cache Star Schema Benchmark – Scale Factor 1 – Mysql 5.5 vs 5.6 …buffer pool (the buffer pool is smaller than the working set) having innodb_old_blocks_time=1000 appears …
Post: MySQL opening .frm even when table is in table definition cache
November 21, 2011 By 8 Comments
… instance of MySQL with 100 tables and the table_definition_cache set to 1000. My understanding of this is that MySQL won’t… example of how this is used is that in the DROP TABLE code path, MySQL uses this magic byte to work out which… it already has cached (often at least twice – in InnoDB itself and in the table_definition_cache). Further reading: MySQL Forge Internals document…
